Cut chicken into serving pieces. Melt butter in a deep skillet. Add the chicken and onions. Cook about 15 minutes turning frequently. Add the curry powder and cook for 3-4 minutes. Add the mushrooms and cook 3-4 additional minutes. Stir in the cream, cayenne pepper, salt and lemon juice and cover the pan. Place in 350° oven and cook for about 30 minutes or until chicken is tender. Serve with rice or small, new potatoes.